The present invention relates to a dialysis method and apparatus therefor, particularly to improvement of a dialysis method and apparatus of the filter press type in which diffusion dialysis or electrodialysis of waste water or solutions carried out by using ion exchange membranes.
Dialysis apparatus of this kind are widely used for concentration of sea water, removing salts from saline water, and treating salt-containing waste water. In the dialysis apparatus of the filter press type, cation exchange membranes and anion exchange membranes are arranged alternately, frame members each are disposed therebetween, and all of them are clamped as in the case of a filter press to maintain a water-tight state therebetween, so that dilution chambers and concentration chambers are defined alternately in the interiors of the frame members. In order to reduce electric resistance of liquid between adjacent ion exchange membranes and maintain the electric current efficiency at a high level, it is preferred that the space between two adjacent membranes be as small as possible, and in now available apparatus, the membrane space is adjusted to 0.5 mm to 2 mm.
When a liquid containing large quantities of suspended substances, such as waste water and sea water, is dialyzed by use of such a conventional dialysis apparatus, scale-forming substances such as suspended substances and gypsum are deposited and accumulated on membrane surfaces or spacers, which spacers are disposed between the membranes for prevention of contacts of them, to cause such troubles as contamination of membranes and clogging in the dialysis chambers, liquid supply holes, and liquid discharge holes. As a result, the operation becomes often impossible to continue, and membrane life is shortened, therefore, it is desired that contamination and clogging be prevented effectively and economically.